Method for preventing abnormality during wireless charging

ABSTRACT

Disclosed is a control method of a wireless power transmitter, including transmitting power to a plurality of wireless power receivers based on a first power value required by a first wireless power receiver from among the plurality of wireless power receivers, selecting, before reaching a threshold condition in which a system error occurs in the wireless power transmitter, a second wireless power receiver from among the plurality of wireless power receivers, and in response to the second wireless power receiver being selected, transmitting power to the plurality of wireless power receivers based on a second power value required by the second wireless power receiver, wherein the system error comprises at least one of an over-temperature error, an over-current error, and an over-voltage error.

PRIORITY

This is a Continuation Application of U.S. patent application Ser. No. 15/720,740, filed with the U.S. Patent and Trademark Office on Sep. 29, 2017, which is a Continuation Application of U.S. patent application Ser. No. 14/627,710, filed with the U.S. Patent and Trademark Office on Feb. 20, 2015, now U.S. Pat. No. 9,787,365, issued on Oct. 10, 2017, and claims priority under 35 U.S.C. § 119(a) to a Korean Patent Application filed on Feb. 20, 2014 in the Korean Intellectual Property Office and assigned Serial No. 10-2014-0019941, the content of each of which is incorporated herein by reference.

BACKGROUND 1. Field of the Invention

The present invention relates generally to wireless charging, and more particularly, to a method for preventing an abnormality during wireless charging.

2. Description of the Related Art

In view of their nature, mobile terminals such as portable phones and Personal Digital Assistants (PDAs) are powered by rechargeable batteries. To charge the batteries, the mobile terminals apply electrical energy to the batteries via chargers. Typically, the charger and the battery each have an exterior contact terminal and thus are electrically connected to each other by contacting their contact terminals.

This contact-based charging scheme faces the problem of vulnerability of contact terminals to contamination by foreign materials and the resulting unreliable battery charging because the contact terminals protrude outward. Moreover, if the contact terminals are exposed to moisture, the batteries may not be charged properly.

To address the above problem, wireless charging or contactless charging has recently been developed and applied to many electronic devices.

Such wireless charging is based on wireless power transmission and reception. For example, once a portable phone is placed on a charging pad without being connected to an additional charging connector, its battery is automatically charged. Among wirelessly charged products, wireless electric toothbrushes or wireless electric shavers are well known. Wireless charging offers the benefits of increased waterproofness due to wireless charging of electronic products and enhanced portability due to no need for a wired charger for electronic devices. Further, it is expected that wireless charging will be more developed for electric vehicles.

There are three wireless charging schemes: electromagnetic induction using coils, resonance-based wireless charging, and Radio Frequency (RF)/microwave radiation based on the conversion of electrical energy to microwaves.

To date, the electromagnetic induction-based wireless charging scheme has been most popular. However, considering recent successful experiments in wireless power transmission over microwaves at a distance of tens of meters in Korea and other overseas countries, it is foreseeable that every electronic product will be charged wirelessly at any time in any place in the near future.

Electromagnetic induction-based power transmission refers to power transfer between primary and secondary coils. When a magnet moves through a coil, current is induced. Based on this principle, a transmitter creates a magnetic field and a receiver produces energy by current induced by a change in the magnetic field. This phenomenon is called magnetic induction and power transmission based on magnetic induction is highly efficient in energy transfer.

A resonance-based wireless charging system has achieved wireless energy transfer from a charger at a distance of a few meters based on the resonance-based power transmission principle by the Coupled Mode Theory. The resonated electromagnetic waves carried electric energy instead of sound. The resonant electrical energy is directly transferred only in the presence of a device having the same resonant frequency, while the unused electrical energy is reabsorbed into the electromagnetic field rather than being dispersed into the air. Thus, the resonant electrical energy does not affect machines or human beings, as compared to other electronic waves.

Wireless charging is an active research area. Thus, there is a need for developing a standard regarding wireless charging priority, detection of a wireless power transmitter/receiver, communication frequency selection between a wireless power transmitter and a wireless power receiver, wireless power control, selection of a matching circuit, and allocation of a communication time to each wireless power receiver in a single charging cycle. Particularly, there exists a need for developing standards for a configuration and procedure that allow a wireless power receiver to select a wireless power transmitter from which to receive wireless power.

A single wireless power transmitter can supply charging power to a plurality of wireless power receivers. Because the plurality of wireless power receivers are different in terms of characteristics, states, and types, various algorithms may be performed to determine transmission power of the wireless power transmitter.

If an abnormality occurs in at least one wireless power receiver during wireless charging with transmission power determined according to a specific algorithm in the wireless power transmitter, the wireless charging may fail.

For example, a wireless power transmitter or a wireless power receiver may be placed in an error situation such as over voltage, over current, or over temperature due to a specific algorithm or some defect in the wireless power receiver.

If the error situation is not self-corrected, the wireless power transmitter may enter a latch fault mode in which it is powered off and prompts a user to reset it, in order to protect the wireless power transmitter or each wireless power receiver which is being charged.

However, if the wireless power transmitter enters the latch fault mode, the user is required to solve the problem, which is not favorable in terms of User eXperience (UX).

Accordingly, there is a need for a self-correcting method for preventing an abnormal situation from developing to an extreme in a system.

SUMMARY

The present invention has been made to address at least the above-mentioned problems and/or disadvantages, and to provide at least the advantages described below.

An aspect of the present invention provides a control method of a wireless power transmitter, including transmitting power to a plurality of wireless power receivers based on a first power value required by a first wireless power receiver from among the plurality of wireless power receivers, selecting, before reaching a threshold condition in which a system error occurs in the wireless power transmitter, a second wireless power receiver from among the plurality of wireless power receivers, and in response to the second wireless power receiver being selected, transmitting power to the plurality of wireless power receivers based on a second power value required by the second wireless power receiver, wherein the system error comprises at least one of an over-temperature error, an over-current error, and an over-voltage error.

Another aspect of the present invention provides a wireless power transmitter for wirelessly charging a plurality of wireless power receivers, including a power transmitter configured to wirelessly transmit power to the plurality of wireless power receivers based on a first power value required by a first wireless power receiver, a communication unit configured to transmit a signal to the plurality of wireless power receivers, and a controller configured to select, before reaching a threshold condition in which a system error occurs in the wireless power transmitter, a second wireless power receiver from among the plurality of wireless power receivers, and in response to the second wireless power receiver being selected, control the power transmitter to transmit power to the plurality of wireless power receivers based on a second power value required by the second wireless power receiver, wherein the system error comprises at least one of an over-temperature error, an over-current error, and an over-voltage error.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of the present invention will be more apparent from the following description, taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a block diagram illustrating an overall operation of a wireless charging system;

FIG. 2 is a block diagram illustrating a wireless power transmitter and a wireless power receiver according to an embodiment of the present invention;

FIG. 3 is a block diagram illustrating a wireless power transmitter and a wireless power receiver according to an embodiment of the present invention;

FIG. 4 is a diagram illustrating a signal flow for operations of a wireless power transmitter and a wireless power receiver according to an embodiment of the present invention;

FIG. 5 is a flowchart illustrating a signal flow for operations of a wireless power transmitter and a wireless power receiver according to another embodiment of the present invention;

FIG. 6 is a graph illustrating amounts of power applied by a wireless power transmitter with respect to a time axis;

FIG. 7 is a flowchart illustrating a method for controlling a wireless power transmitter according to an embodiment of the present invention;

FIG. 8 is a graph illustrating amounts of power applied by a wireless power transmitter with respect to a time axis according to FIG. 7;

FIG. 9 is a flowchart illustrating a method for controlling a wireless power transmitter according to an embodiment of the present invention;

FIG. 10 is a graph illustrating amounts of power supplied by a wireless power transmitter with respect to a time axis according to FIG. 9;

FIG. 11 is a block diagram illustrating a wireless power transmitter and a wireless power receiver in a Stand Alone (SA) mode according to an embodiment of the present invention;

FIG. 12 is a flowchart illustrating an operation for preventing an abnormality during wireless charging according to an embodiment of the present invention;

FIG. 13 is a flowchart illustrating an operation for preventing an abnormality during wireless charging according to an embodiment of the present invention;

FIG. 14 is a flowchart illustrating an operation for preventing an abnormality during wireless charging according to an embodiment of the present invention; and

FIG. 15 is a flowchart illustrating an operation for preventing an abnormality during wireless charging according to an embodiment of the present invention

DETAILED DESCRIPTION OF EMBODIMENTS OF THE PRESENT INVENTION

The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of embodiments of the present invention as defined by the appended claims and their equivalents. It includes details to assist in that understanding but these are to be regarded as mere examples. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments of the present invention described herein can be made without departing from the scope and spirit of the present invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness. Throughout the drawings, like reference numerals will be understood to refer to like parts, components, and structures.

The terms and words used in the following description and claims are not limited to their dictionary meanings, but are merely used to enable a clear and consistent understanding of the present invention. Accordingly, it should be apparent to those skilled in the art that the following description of embodiments of the present invention is provided for illustration purposes only and not for the purpose of limiting the present invention as defined by the appended claims and their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a component surface” includes reference to one or more of such surfaces.

The term “substantially” refers to a recited characteristic, parameter, or value that need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.

A description is first given of the concept of a wireless charging system applicable to embodiments of the present invention with reference to FIGS. 1 to 11, followed by a detailed description of methods for preventing an abnormality during wireless charging according to various embodiments of the present invention with reference to FIGS. 12 to 15.

FIG. 1 is a block diagram illustrating an overall operation of a wireless charging system.

Referring to FIG. 1, the wireless charging system includes a wireless power transmitter (or Power Transmitting Unit (PTU)) 100 and one or more wireless power receivers (or Power Receiving Units (PRUs)) 110-1, 110-2, . . . , and 110-n.

The wireless power transmitter 100 wirelessly transmits power 1-1, 1-2, . . . , and 1-n, respectively, to the wireless power receivers 110-1, 110-2, . . . , and 110-n. More specifically, the wireless power transmitter 100 may wirelessly transmit the power 1-1, 1-2, . . . , and 1-n only to wireless power receivers that have been authenticated in a predetermined authentication procedure.

The wireless power transmitter 100 establishes electrical connections to the wireless power receivers 110-1, 110-2, . . . , and 110-n. For example, the wireless power transmitter 100 transmits wireless power in the form of electromagnetic waves to the wireless power receivers 110-1, 110-2, . . . , and 110-n.

The wireless power transmitter 100 conducts bi-directional communication with the wireless power receivers 110-1, 110-2, . . . , and 110-n. The wireless power transmitter 100 and the wireless power receivers 110-1, 110-2, . . . , and 110-n process or transmit/receive packets 2-1, 2-2, . . . , and 2-n configured in predetermined frames. The frames will be described below in greater detail. A wireless power receiver 110-1, 110-2, . . . , 110-n may be configured as a mobile communication terminal, a Personal Digital Assistant (PDA), a Personal Multimedia Player (PMP), a smartphone, or the like.

The wireless power transmitter 100 applies power wirelessly to the plurality of wireless power receivers 110-1, 110-2, . . . , and 110-n. For example, the wireless power transmitter 100 transmits power to the plurality of wireless power receivers 110-1, 110-2, . . . , and 110-n by resonance. If the wireless power transmitter 100 adopts the resonance scheme, the distance between the wireless power transmitter 100 and the wireless power receivers 110-1, 110-2, . . . , and 110-n may be 30 m or smaller. If the wireless power transmitter 100 adopts an electromagnetic induction scheme, the distance between the wireless power transmitter 100 and the wireless power receivers 110-1, 110-2, . . . , and 110-n may be 10 cm or smaller.

The wireless power receivers 110-1, 110-2, . . . , and 110-n receive wireless power from the wireless power transmitter 100 and charge their internal batteries. Further, the wireless power receivers 110-1, 110-2, . . . , and 110-n transmit to the wireless power transmitter 100 a signal requesting wireless power transmission, information required for wireless power reception, wireless power receiver state information, or control information for the wireless power transmitter 100. Information of the transmitted signal is described below in greater detail.

Each of the wireless power receivers 110-1, 110-2, . . . , and 110-n also transmits a message indicating its charged state to the wireless power transmitter 100.

The wireless power transmitter 100 includes a display means such as a display and displays the state of each wireless power receiver 110-1, 110-2, . . . , 110-n based on the messages received from the wireless power receivers 110-1, 110-2, . . . , and 110-n. Further, the wireless power transmitter 100 displays a time when it is expected that each of the wireless power receivers 110-1, 110-2, . . . , and 110-n will be completely charged.

The wireless power transmitter 100 transmits a control signal for disabling a wireless charging function to the wireless power receivers 110-1, 110-2, . . . , and 110-n. Upon receipt of the control signal for disabling the wireless charging function from the wireless power transmitter 100, a wireless power receiver 110-1, 110-2, . . . , 110-n disables the wireless charging function.

FIG. 2 is a block diagram illustrating a wireless power transmitter 200 and a wireless power receiver 250 according to an embodiment of the present invention.

Referring to FIG. 2, the wireless power transmitter 200 includes at least one of a power transmission unit 211, a controller 212, a communication unit 213, a display unit 214, and a storage unit 215.

The power transmission unit 211 supplies power required for the wireless power transmitter 200 and wirelessly supplies power to the wireless power receiver 250. The power transmission unit 211 supplies power in the form of Alternate Current (AC) waveforms or by converting power in Direct Current (DC) waveforms to power in AC waveforms by means of an inverter. The power transmission unit 211 may be implemented as a built-in battery. Alternatively, the power transmission units 211 may be implemented as a power reception interface so as to receive power from externally and supply the power to other components. It will be understood by those skilled in the art that as far as it can supply power in AC waveforms, any means may be used as the power transmission unit 211.

The controller 212 provides overall control to the wireless power transmitter 200. The controller 212 controls the overall operation of the wireless power transmitter 200 using an algorithm, a program, or an application required for a control operation, read from the storage unit 215. The controller 212 may be configured as a Central Processing Unit (CPU), a microprocessor, or a mini computer.

The communication unit 213 communicates with the wireless power receiver 250 in a predetermined communication scheme. The communication unit 213 receives power information from the wireless power receiver 250. The power information includes information about at least one of the capacity, residual battery amount, use amount, battery capacity, and battery proportion of the wireless power receiver 250.

Further, the communication unit 213 transmits a charging function control signal for controlling the charging function of the wireless power receiver 250. The charging function control signal is a control signal that enables or disables the charging function by controlling a power reception unit 251 of the wireless power receiver 250. Alternatively, the power information includes information about insertion of a wired charging terminal, transition from a Stand Alone (SA) mode to a Non-Stand Alone (NSA) mode, error state release, and the like, as described below in detail.

In addition, the charging function control signal includes information related to power control or a power adjust command to cope with an occurrence of an abnormality according to an embodiment of the present invention.

The communication unit 213 may receive a signal from another wireless power transmitter as well as the wireless power receiver 250.

The controller 212 displays a state of the wireless power receiver 250 on the display unit 214 based on a message received from the wireless power receiver 250 via the communication unit 213. Further, the controller 212 displays a time by which the wireless power receiver 250 is expected to be completely charged, on the display unit 214.

As illustrated in FIG. 2, the wireless power receiver 250 includes at least one of a power reception unit 251, a controller 252, a communication unit 253, a display unit 258, and a storage unit 259.

The power reception unit 251 receives power wirelessly from the wireless power transmitter 200. The power reception unit 251 receives power in the form of AC waveforms from the wireless power transmitter 200.

The controller 252 provides overall control to the wireless power receiver 250. The controller 252 controls the overall operation of the wireless power receiver 250 using an algorithm, a program, or an application required for a control operation, read from the storage unit 259. The controller 252 may be configured as a CPU, a microprocessor, or a mini computer.

The communication unit 253 communicates with the wireless power transmitter 200 in a predetermined communication scheme. The communication unit 253 transmits power information to the wireless power transmitter 200. The power information includes information about at least one of the capacity, residual battery amount, use amount, battery capacity, and battery proportion of the wireless power receiver 250.

Further, the communication unit 253 transmits a charging function control signal for controlling the charging function of the wireless power receiver 250. The charging function control signal is a control signal that enables or disables the charging function by controlling the power reception unit 251 of the wireless power receiver 250. Alternatively, the power information includes information about insertion of a wired charging terminal, transition from the SA mode to the NSA mode, error state release, and the like, as described below in detail.

Further, the charging function control signal includes information related to power control or a power adjust command to cope with an occurrence of an abnormality according to an embodiment of the present invention.

The controller 252 displays a state of the wireless power receiver 250 on the display unit 258. Further, the controller 252 displays a time by which the wireless power receiver 250 is expected to be completely charged, on the display unit 258.

FIG. 3 is a block diagram illustrating the wireless power transmitter 200 and the wireless power receiver 250 according to an embodiment of the present invention.

Referring to FIG. 3, the wireless power transmitter 200 includes at least one of a Transmission (Tx) resonator 211 a, the controller 212 (for example, a Micro Controller Unit (MCU)), the communication unit 213 (for example, an out-of-band signaling unit), a matching unit 216, a driver (e.g. a power supply) 217, a Power Amplifier (PA) 218, and a sensing unit 219. The wireless power receiver 250 includes at least one of a Reception (Rx) resonator 251 a, the controller 252, the communication unit 253, a rectifier 254, a DC/DC converter 255, a switching unit 256, and a loading unit 257.

The driver 217 outputs DC power having a predetermined voltage value. The voltage value of the DC power output from the driver 217 is controlled by the controller 212.

A DC current output from the driver 217 is applied to the PA 218. The PA 218 amplifies the DC current with a predetermined gain. Further, the PA 218 converts DC power to AC power based on a signal received from the controller 212. Therefore, the PA 218 outputs AC power.

The matching unit 216 performs impedance matching. For example, the matching unit 216 controls an impedance viewed from the matching unit 216 so that its output power has high efficiency or high power. The sensing unit 219 senses a load variation of the wireless power receiver 250 via the Tx resonator 211 a or the PA 218 and provides the sensing result to the controller 212.

The matching unit 216 adjusts impedance under control of the controller 212. The matching unit 216 includes at least one of a coil and a capacitor. The controller 212 controls a connection state to at least one of the coil and the capacitor and thus may perform impedance matching accordingly.

The Tx resonator 211 a transmits input AC power to the Rx resonator 251 a. The Tx resonator 211 a and the Rx resonator 251 a are configured as resonant circuits having the same resonant frequency. For example, the resonant frequency may be determined to be 6.78 MHz.

The communication unit 213 communicates with the communication unit 253 of the wireless power receiver 250, for example, bi-directionally at 2.4 GHz (by Wireless Fidelity (WiFi), ZigBee, or Bluetooth (BT)/Bluetooth Low Energy (BLE)).

The Rx resonator 251 a receives power for charging.

The rectifier 254 rectifies wireless power received from the Rx resonator 251 a to DC power. For example, the rectifier 254 may be configured as a bridge diode. The DC/DC converter 255 converts the rectified power with a predetermined gain. For example, the DC/DC converter 255 converts the rectified power so that the voltage of its output may be 5V. A minimum voltage value and a maximum voltage value that may be applied to the input of the DC/DC converter 255 may be preset.

The switching unit 256 connects the DC/DC converter 255 to the loading unit 257. The switching unit 256 is kept in an ON or OFF state under the control of the controller 252. The switching unit 256 may be omitted. If the switching unit 256 is in the ON state, the loading unit 257 stores the converted power received from the DC/DC converter 255.

FIG. 4 is a diagram illustrating a signal flow for operations of a wireless power transmitter 400 and a wireless power receiver 450 according to an embodiment of the present invention.

Referring to FIG. 4, the wireless power transmitter 400 is powered ON, in step S401. Upon power-on, the wireless power transmitter 400 configures an environment, in step S402.

The wireless power transmitter 400 enters a power save mode, in step S403. In the power save mode, the wireless power transmitter 400 applies different types of power beacons for detection, with their respective periods, which will be described below in greater detail with reference to FIG. 6. For example, the wireless power transmitter 400 transmits power beacons 404 and 405 for detection (for example, short beacons or long beacons) and the power beacons 404 and 405 may have different power values. One or both of the power beacons 404 and 405 for detection may have sufficient power to drive the communication unit of the wireless power receiver 450. For example, the wireless power receiver 450 communicates with the wireless power transmitter 400 by driving its communication unit by means of one or both of the power beacons 404 and 405 for detection. This state may be referred to as a null state.

The wireless power transmitter 400 detects a load variation caused by disposition of the wireless power receiver 450. The wireless power transmitter 400 enters a low power mode, in step S408. The low power mode is described below in greater detail with reference to FIG. 6. The wireless power receiver 450 drives the communication unit with power received from the wireless power transmitter 400, in step S409.

The wireless power receiver 450 transmits a PTU searching signal to the wireless power transmitter 400, in step S410. The wireless power receiver 450 may transmit the PTU searching signal by a BLE-based Advertisement (AD) signal. The wireless power receiver 450 may transmit the PTU searching signal periodically until it receives a response signal from the wireless power transmitter 400 or a predetermined time period lapses.

Upon receipt of the PTU searching signal from the wireless power receiver 450, the wireless power transmitter 400 transmits a PRU response signal, in step S411. The PRU response signal establishes a connection between the wireless power transmitter 400 and the wireless power receiver 450.

The wireless power receiver 450 transmits a PRU static signal, in step S412. The PRU static signal indicates a state of the wireless power receiver 450 and requests joining in a wireless power network managed by the wireless power transmitter 400.

The wireless power transmitter 400 transmits a PTU static signal, in step S413. The PTU static signal indicates capabilities of the wireless power transmitter 400.

Once the wireless power transmitter 400 and the wireless power receiver 450 transmit and receive the PRU static signal and the PTU static signal, the wireless power receiver 450 transmits a PRU dynamic signal periodically, in steps S414 and S415. The PRU dynamic signal includes at least one parameter measured by the wireless power receiver 450. For example, the PRU dynamic signal may include information about a voltage at the output of a rectifier of the wireless power receiver 450. The state of the wireless power receiver 450 may be referred to as a boot state, in step S407.

The wireless power transmitter 400 enters a power transfer mode, in step S416. The wireless power transmitter 400 transmits a PRU control signal commanding charging to the wireless power receiver 450, in step S417. In the power transfer mode, the wireless power transmitter 400 transmits charging power.

The PRU control signal transmitted by the wireless power transmitter 400 includes information that enables/disables charging of the wireless power receiver 450 and permission information. The PRU control signal may be transmitted each time a charged state is changed. For example, the PRU control signal may be transmitted every 250 ms or upon occurrence of a parameter change. The PRU control signal may be configured to be transmitted within a predetermined threshold time, for example, within 1 second, even though no parameter is changed.

The wireless power receiver 450 changes a setting according to the PRU control signal and transmits a PRU dynamic signal to report a state of the wireless power receiver 450, in step S418 and S419. The PRU dynamic signal transmitted by the wireless power receiver 450 includes information about at least one of a voltage, a current, a wireless power receiver state, and a temperature. The state of the wireless power receiver 450 may be referred to as an ON state.

The PRU dynamic signal may have the following data structure illustrated in Table 1 below.

TABLE 1 Field Octets Description Use Units Optional fields 1 Defines which optional fields Mandatory are populated V_(RECT) 2 Voltage at diode output Mandatory mV I_(RECT) 2 Current at diode output Mandatory mA V_(OUT) 2 Voltage at charge/battery port Optional mV I_(OUT) 2 Current at charge/battery port Optional mA Temperature 1 Temperature of PRU Optional Deg C. from −40 C. V_(RECT) _(—) _(MIN) _(—) _(DYN) 2 V_(RECT) _(—) _(LOW) _(—) _(LIMIT) Optional mV (dynamic value) V_(RECT) _(—) _(SET) _(—) _(DYN) 2 Desired V_(RECT) Optional mV (dynamic value) V_(RECT) _(—) _(HIGH) _(—) _(DYN) 2 V_(RECT) _(—) _(HIGH) _(—) _(LIMIT) Optional mV (dynamic value) PRU alert 1 Warnings Mandatory Bit field RFU 3 Undefined

Referring to Table 1, the PRU dynamic signal includes one or more fields. The fields provide optional field information, information about a voltage at the output of the rectifier of the wireless power receiver, information about a current at the output of the rectifier of the wireless power receiver, information about a voltage at the output of the DC/DC converter of the wireless power receiver, information about a current at the output of the DC/DC converter of the wireless power receiver, temperature information, information about a minimum voltage value VRECT_MIN_DYN at the output of the rectifier of the wireless power receiver, information about an optimum voltage value VRECT_SET_DYN at the output of the rectifier of the wireless power receiver, information about a maximum voltage value VRECT_HIGH_DYN at the output of the rectifier of the wireless power receiver, and warning information. The PRU dynamic signal may include at least one of the above fields.

For example, at least one voltage set value that has been determined according to a charging situation (for example, the information about a minimum voltage value VRECT_MIN_DYN at the output of the rectifier of the wireless power receiver, the information about an optimum voltage value VRECT_SET_DYN at the output of the rectifier of the wireless power receiver, and the information about a maximum voltage value VRECT_HIGH_DYN at the output of the rectifier of the wireless power receiver) may be transmitted in the at least one field of the PRU dynamic signal. Upon receipt of the PRU dynamic signal, the wireless power transmitter may adjust a wireless charging voltage to be transmitted to each wireless power receiver based on the voltage value set in the PRU dynamic signal.

Among the fields, PRU Alert may be configured in the data structure illustrated in Table 2.

TABLE 2 7 6 5 4 3 2 1 0 Overvoltage Overcurrent Overtemp Charge TA Transition restart RFU complete detect request

Referring to Table 2, PRU Alert may include a bit for a restart request, a bit for a transition, and a bit for Travel Adapter (TA) detect. The TA detect bit indicates that a wireless power receiver has been connected to a wired charging terminal in the wireless power transmitter that provides wireless charging. The Transition bit indicates to the wireless power transmitter that a communication Integrated Circuit (IC) of the wireless power receiver is reset before the wireless power receiver transitions from the SA mode to the NSA mode. Finally, the restart request bit indicates that the wireless power transmitter is ready to resume charging of the wireless power receiver when the wireless power transmitter that has discontinued charging by reducing transmission power due to over current or over temperature returns to a normal state.

PRU Alert may also be configured in the data structure illustrated in Table 3 below.

TABLE 3 7 6 5 4 3 2 1 0 PRU PRU PRU PRU Self Charge Wired Mode Mode over- over- over- Protection Complete Charger Transition Transition voltage current temperature Detect Bit 1 Bit 0

Referring to Table 3, PRU Alert includes the fields of over voltage, over temperature, PRU Self Protection, Charge Complete, Wired Charger Detect, and Mode Transition. If the over voltage field is set to “1”, this implies that the voltage Vrect of the wireless power receiver has exceeded an over voltage limit. The over current and over temperature fields may be set in the same manner as the over voltage field. PRU Self Protection refers to the wireless power receiver protecting itself by directly reducing power affecting a load. In this case, the wireless power transmitter does not need to change a charged state.

According to an embodiment of the present invention, bits for Mode Transition are set to a value indicating the duration of a mode transition to the wireless power transmitter. The Mode Transition bits may be configured as illustrated in Table 4.

TABLE 4 Value(Bit) Mode Transition Bit Description 00 No Mode Transition 01 2 s Mode Transition time limit 10 3 s Mode Transition time limit 11 6 s Mode Transition time limit

Referring to Table 4, if the Mode Transition bits are set to “00”, this indicates no mode transition. If the Mode Transition bits are set to “01”, this indicates that a time limit for completion of a mode transition is 2 seconds. If the Mode Transition bits are set to “10”, this indicates that the time limit for completion of a mode transition is 3 seconds. If the Mode. Transition bits are set to “11”, this indicates that the time limit for completion of a mode transition is 6 seconds.

For example, if a mode transition takes 3 seconds or less, the Mode Transition bits may be set to “10”. Before starting a mode transition, the wireless power receiver ensures that no impedance shift will occur during the mode transition by changing an input impedance setting to match a 1.1 W power draw. Accordingly, the wireless power transmitter adjusts a power ITX_COIL for the wireless power receiver according to this setting and thus maintains the power ITX_COIL for the wireless power receiver during the mode transition.

Therefore, once a mode transition duration is set by the Mode Transition bits, the wireless power transmitter maintains the power ITX_COIL for the wireless power receiver during the mode transition duration, for example, for 3 seconds. In other words, even though the wireless power transmitter does not receive a response from the wireless power receiver for 3 seconds, the wireless power transmitter maintains a connection to the wireless power receiver. However, after the mode transition duration lapses, the wireless power transmitter ends the power transmission, considering that the wireless power receiver is a rogue object.

The wireless power receiver 450 senses generation of an error. The wireless power receiver 450 transmits a warning signal to the wireless power transmitter 400, in step S420. The warning signal may be transmitted by a PRU dynamic signal or an alert signal. For example, the wireless power receiver 450 may transmit the PRU Alert field illustrated in Table 1 to indicate an error state to the wireless power transmitter 400. Alternatively, the wireless power receiver 450 may transmit a stand-alone warning signal indicating an error state to the wireless power transmitter 400. Upon receipt of the warning signal, the wireless power transmitter 400 enters a latch fault mode, in step S422. The wireless power receiver 450 enters a null state, in step S423.

FIG. 5 is a flowchart illustrating a signal flow for operations of a wireless power transmitter and a wireless power receiver according to an embodiment of the present invention. The control method of FIG. 5 is described below in detail with reference to FIG. 6.

FIG. 6 is a graph illustrating amounts of power applied by the wireless power transmitter with respect to a time axis.

Referring to FIG. 5, the wireless power transmitter starts to operate, in step S501. Further, the wireless power transmitter rests an initial setting, in step S503 and enters the power save mode, in step S505. The wireless power transmitter applies different types of power having different power amounts to a power transmitter in the power save mode. For example, the wireless power transmitter may apply second detection power 601 and 602 and third detection power 611 to 615 to the power transmitter in FIG. 6. The wireless power transmitter may apply the second detection power 601 and 602 periodically with a second period. When the wireless power transmitter supplies the second detection power 601 and 602, the second detection power 601 and 602 may last for a second time duration. The wireless power transmitter may apply the third detection power 611 to 615 periodically with a third period. When the wireless power transmitter supplies the third detection power 611 to 615, the third detection power 611 to 615 may last for a third time duration. The third detection power 611 to 615 may have the same power value, or different power values as illustrated in FIG. 6.

After outputting the third detection power 611, the wireless power transmitter outputs the third detection power 612 having the same power amount. If the wireless power transmitter outputs third detection power having the same amount as described above, the third detection power may have a power amount sufficient to detect the smallest wireless power receiver, for example, a wireless power receiver of Category 1.

In contrast, after outputting the third detection power 611, the wireless power transmitter may output the third detection power 612 having a different power amount. If the wireless power transmitter outputs different amounts of third detection power as described above, the respective power amounts of the third detection power may be sufficient to detect wireless power receivers of Category 1 to Category 5. For example, the third detection power 611 may have a power amount sufficient to detect a wireless power receiver of Category 5, the third detection power 612 may have a power amount sufficient to detect a wireless power receiver of Category 3, and the third detection power 613 may have a power amount sufficient to detect a wireless power receiver of Category 1.

The second detection power 601 and 602 may drive the wireless power receiver. More specifically, the second detection power 601 and 602 may have a power amount sufficient to drive the controller and/or the communication unit of the wireless power receiver.

The wireless power transmitter may apply the second detection power 601 and 602 and the third detection power 611 to 615 respectively with the second and third periods to the wireless power receiver. If the wireless power receiver is placed on the wireless power transmitter, impedance viewed from the wireless power transmitter may be changed. The wireless power transmitter may detect an impedance shift during application of the second detection power 601 and 602 and the third detection power 611 to 615. For example, the wireless power transmitter may detect an impedance shift during application of the third detection power 615. Therefore, the wireless power transmitter may detect an object, in step S507. If no object is detected, in step S507, e.g. NO, the wireless power transmitter is kept in the power save mode in which it applies different types of power periodically, in step S505.

If the wireless power transmitter detects an object due to an impedance shift, in step S507, e.g. YES, the wireless power transmitter enters the low power mode. In the low power mode, the wireless power transmitter applies a driving power having a power amount sufficient to drive the controller and the communication unit of the wireless power receiver. For example, the wireless power transmitter applies driving power 620 to the power transmitter in FIG. 6. The wireless power receiver receives the driving power 620 and drives the controller and/or the communication unit with the driving power 620. The wireless power receiver communicates with the wireless power transmitter with the driving power 620 in a predetermined communication scheme. For example, the wireless power receiver may transmit and receive data required for authentication and may join a wireless power network managed by the wireless power transmitter based on the data. However, if a rogue object is placed instead of a wireless power receiver, data transmission and reception are not performed. Therefore, the wireless power transmitter determines whether the object is a rogue object, in step S511. For example, if the wireless power transmitter fails to receive a response from the object for a predetermined time, the wireless power transmitter determines the object to be a rogue object.

If the wireless power transmitter determines the object to be a rogue object, in step S511, e.g. YES, the wireless power transmitter enters the latch fault mode, in step S513. In contrast, if the wireless power transmitter determines that the object is not a rogue object, in step S511, e.g., NO, the wireless power transmitter may proceeds to a joining operation, in step S519. For example, the wireless power transmitter may apply first power 631 to 634 periodically with a first period in FIG. 6. The wireless power transmitter may detect an impedance shift during application of the first power. For example, if the rogue object is removed, in step S515, e.g. YES, the wireless power transmitter detects an impedance shift and thus determines that the rogue object has been removed. In contrast, if the rogue object is not removed, in step S515, e.g. NO, the wireless power transmitter does not detect an impedance shift and thus determines that the rogue object has not been removed. If the rogue object has not been removed, the wireless power transmitter notifies a user that the wireless power transmitter is currently in an error state by performing at least one of illuminating a lamp or outputting a warning sound. Accordingly, the wireless power transmitter includes an output unit for illuminating a lamp and/or outputting a warning sound.

If determining that the rogue object has not been removed, in step S515, e.g. NO, the wireless power transmitter maintains the latch fault mode, in step S513. In contrast, if the rogue object has been removed, in step S515, e.g. YES, the wireless power transmitter reenters the power save mode, in step S517. For example, the wireless power transmitter may apply second power 651 and 652 and third power 661 to 665 in FIG. 6.

As described above, if a rogue object is placed on the wireless power transmitter, instead of a wireless power receiver, the wireless power transmitter enters the latch fault mode. Further, the wireless power transmitter determines whether the rogue object has been removed based on an impedance shift that occurs according to power applied in the latch fault mode. That is, a condition of entry to the latch fault mode is the presence of a rogue object in the embodiment illustrated in FIGS. 5 and 6. Besides the presence of a rogue object, the wireless power transmitter may have many other conditions for entry to the latch fault mode. For example, the wireless power transmitter may be cross-connected to a mounted wireless power receiver. In this case, the wireless power transmitter also enters the latch fault mode.

When the wireless power transmitter is cross-connected to a wireless power receiver, the wireless power transmitter must return to an initial state and the wireless power receiver should be removed. The wireless power transmitter may set cross connection of a wireless power receiver placed on another wireless power transmitter, that is, joining of a wireless power receiver placed on another wireless power transmitter in a wireless power network managed by the wireless power transmitter, as a condition for entry to the latch fault mode. An operation of a wireless power transmitter upon occurrence of an error such as cross connection is described below with reference to FIG. 7.

FIG. 7 is a flowchart illustrating a method for controlling a wireless power transmitter according to an embodiment of the present invention. The control method of FIG. 7 is described below in detail with reference to FIG. 8.

FIG. 8 is a graph illustrating amounts of power supplied by the wireless power transmitter with respect to a time axis according to the embodiment of the present invention illustrated in FIG. 7.

Referring to FIG. 7, the wireless power transmitter starts to operate, in step S701. Further, the wireless power transmitter may reset an initial setting, in step S703, and may enter the power save mode, in step S705. The wireless power transmitter may apply different types of power having different power amounts to the power transmitter in the power save mode. For example, the wireless power transmitter may apply second detection power 801 and 802 and third detection power 811 to 815 to the power transmitter in FIG. 8. The wireless power transmitter may apply the second detection power 801 and 802 periodically with a second period. When the wireless power transmitter applies the second detection power 801 and 802, the second detection power 801 and 802 lasts for a second time duration. The wireless power transmitter may apply the third detection power 811 to 815 periodically with a third period. When the wireless power transmitter applies the third detection power 811 to 815, the third detection power 811 to 815 lasts for a third time duration. The third detection power 811 to 815 may have the same power value, or different power values as illustrated in FIG. 8.

The second detection power 801 and 802 may drive the wireless power receiver. More specifically, the second detection power 801 and 802 may have a power amount sufficient to drive the controller and/or the communication unit of the wireless power receiver.

The wireless power transmitter may apply the second detection power 801 and 802 and the third detection power 811 to 815 respectively with the second and third periods to the wireless power receiver. If the wireless power receiver is placed on the wireless power transmitter, impedance viewed from the wireless power transmitter may be changed. The wireless power transmitter may detect an impedance shift during application of the second detection power 801 and 802 and the third detection power 811 to 815. For example, the wireless power transmitter may detect an impedance shift during application of the third detection power 815. Therefore, the wireless power transmitter detects an object, in step S707. If no object is detected, in step S707, e.g. NO, the wireless power transmitter is kept in the power save mode in which it applies different types of power periodically, in step S705.

If the wireless power transmitter detects an object due to an impedance shift, in step S707, e.g. YES, the wireless power transmitter enters the low power mode, in step S709. In the low power mode, the wireless power transmitter applies a driving power having a power amount sufficient to drive the controller and/or the communication unit of the wireless power receiver. For example, the wireless power transmitter applies driving power 820 to the power transmitter in FIG. 8. The wireless power receiver receives the driving power 820 and drives the controller and/or the communication unit with the driving power 820. The wireless power receiver communicates with the wireless power transmitter with the driving power 820 in a predetermined communication scheme. For example, the wireless power receiver transmits and receives data required for authentication and joins a wireless power network managed by the wireless power transmitter based on the data.

Subsequently, the wireless power transmitter enters the power transfer mode in which it transmits charging power, in step S711. For example, the wireless power transmitter applies charging power 821 and the charging power 821 is transmitted to the wireless power receiver, as illustrated in FIG. 8.

In the power transfer mode, the wireless power transmitter determines whether an error has occurred. The error may be the presence of a rogue object, cross connection, over voltage, over current, or over temperature. The wireless power transmitter includes a sensing unit for measuring over voltage, over current, or over temperature. For example, the wireless power transmitter measures a voltage or current at a reference point and determines that a measured voltage or current exceeding a threshold satisfies an over voltage or over current condition. Alternatively, the wireless power transmitter includes a temperature sensor, and the temperature sensor measures a temperature at a reference point of the wireless power transmitter. If the temperature at the reference point exceeds a threshold, the wireless power transmitter determines that an over temperature condition is satisfied.

If the wireless power transmitter determines an over voltage, over current, or over temperature state according to a measured voltage, current, or temperature value, the wireless power transmitter prevents over voltage, over current, or over temperature by decreasing wireless charging power by a predetermined value. If the voltage value of the decreased wireless charging power is below a set minimum value (for example, the minimum voltage value VRECT_MIN_DYN at the output of the rectifier of the wireless power receiver), wireless charging is discontinued and thus a voltage set value is re-adjusted according to an embodiment of the present invention.

While continued presence of a rogue object on the wireless power transmitter is shown as an error in the embodiment of the present invention illustrated in FIG. 8, the error is not limited to the continued presence of a rogue object. Thus, it will be readily understood to those skilled in the art that the wireless power transmitter may operate in a similar manner regarding the presence of a rogue object, cross connection, over voltage, over current, and over temperature.

If no error occurs, in step S713, e.g. NO, the wireless power transmitter maintains the power transfer mode, in step S711. In contrast, if an error occurs, in step S713, e.g. YES, the wireless power transmitter enters the latch fault mode, in step S715. For example, the wireless power transmitter applies first power 831 to 835 as illustrated in FIG. 8. Further, the wireless power transmitter outputs an error notification including at least one of lamp illumination or a warning sound during the latch fault mode. If determining that the rogue object or the wireless power receiver has not been removed, in step S717, e.g. NO, the wireless power transmitter maintains the latch fault mode, in step S715. In contrast, if determining that the rogue object or the wireless power receiver has been removed, in step S717, e.g. YES, the wireless power transmitter reenters the power save mode, in step S719. For example, the wireless power transmitter applies second power 851 and 852 and third power 861 to 865 in FIG. 8.

An operation of a wireless power transmitter upon occurrence of an error during transmission of charging power has been described above. Below, a description is provided of an operation of the wireless power transmitter, when a plurality of wireless power receivers placed on the wireless power transmitter receive charging power from the wireless power transmitter.

FIG. 9 is a flowchart illustrating a method for controlling a wireless power transmitter according to an embodiment of the present invention. The control method of FIG. 9 is described below in detail with reference to FIG. 9.

FIG. 10 is a graph illustrating amounts of power applied by the wireless power transmitter with respect to a time axis according to the embodiment of the present invention illustrated in FIG. 9.

Referring to FIG. 9, the wireless power transmitter transmits charging power to a first wireless power receiver, in step S901. The wireless power transmitter also transmits charging power to a second wireless power receiver, in step S905. More specifically, the wireless power transmitter applies the sum of charging power required for the first wireless power receiver and charging power required for the second wireless power receiver to power receivers of the first and second wireless power receivers.

An embodiment of steps S901 to S905 is illustrated in FIG. 10. For example, the wireless power transmitter maintains the power save mode in which the wireless power applies second detection power 1001 and 1002 and third detection power 1011 to 1015. Subsequently, the wireless power transmitter detects the first wireless power receiver and enters the low power mode in which the wireless power transmitter maintains detection power 1020. Then, the wireless power transmitter enters the power transfer mode in which the wireless power transmitter applies first charging power 1030. The wireless power transmitter detects the second wireless power receiver and allows the second wireless power receiver to join the wireless power network. In addition, the wireless power transmitter applies second charging power 1040 being the sum of charging power required for the first wireless power receiver and charging power required for the second wireless power receiver.

Referring to FIG. 9, while transmitting charging power to both the first and second wireless power receivers, in step S905, the wireless power transmitter detects an error, in step S907. As described above, the error may be due to the presence of a rogue object, cross connection, over voltage, over current, or over temperature. If no error occurs, in step S907, e.g., NO, the wireless power transmitter continues to apply second charging power 1040.

In contrast, if an error occurs, in step S907, e.g. YES, the wireless power transmitter enters the latch fault mode, in step S909. For example, the wireless power transmitter applies first power 1051 to 1055 with a first period as illustrated in FIG. 10. The wireless power transmitter determines whether both the first and second wireless power receivers have been removed, in step S911. For example, the wireless power transmitter detects an impedance shift while applying the first power 1051 to 1055. The wireless power transmitter determines whether both the first and second wireless power receivers have been removed by checking whether an impedance has returned to an initial value.

If determining that both the first and second wireless power receivers have been removed, in step S911, e.g. YES, the wireless power transmitter enters the power save mode, in step S913. For example, the wireless power transmitter applies second detection power 1061 and 1062 and third detection power 1071 to 1075 respectively with second and third periods, as illustrated in FIG. 10.

As described above, even though the wireless power transmitter applies charging power to a plurality of wireless power receivers, upon an occurrence of an error, the wireless power transmitter may readily determine whether a wireless power receiver or a rogue object has been removed.

FIG. 11 is a block diagram of a wireless power transmitter and a wireless power receiver in the SA mode according to an embodiment of the present invention.

Referring to FIG. 11, a wireless power transmitter 1100 includes a communication unit 1110, a PA 1120, and a resonator 1130. A wireless power receiver 1150 includes a communication unit 1151, an Application Processor (AP) 1152, a Power Management Integrated Circuit (PMIC) 1153, a Wireless Power Integrated Circuit (WPIC) 1154, a resonator 1155, an Interface Power Management IC (IFPM) 1157, a TA 1158, and a battery 1159.

The communication unit 1110 of the wireless power transmitter 1100 may be configured as a WiFi/BT combo IC and may communicate with the communication unit 1151 in the wireless power receiver 1150 in a predetermined communication scheme, for example, in BLE. For example, the communication unit 1151 of the wireless power receiver 1150 may transmit a PRU dynamic signal having the afore-described data structure illustrated in Table 1 to the communication unit 1110 of the wireless power transmitter 1100. As described above, the PRU dynamic signal may include at least one of voltage information, current information, and temperature information about the wireless power receiver 1150.

An output power value from the PA 1120 may be adjusted based on the received PRU dynamic signal. For example, if over voltage, over current, or over temperature is applied to the wireless power receiver 1150, a power value output from the PA 1120 may be decreased. If the voltage or current of the wireless power receiver 1150 is below a predetermined value, the power value output from the PA 1120 may be increased.

Charging power from the resonator 1130 of the wireless power transmitter 1100 is transmitted wirelessly to the resonator 1155 of the wireless power receiver 1150.

The WPIC 1154 rectifies the charging power received from the resonator 1155 and performs DC/DC conversion on the rectified charging power. The WPIC 1154 drives the communication unit 1151 or charges the battery 1159 with the converted power.

A wired charging terminal may be inserted into the TA 1158. A wired charging terminal such as a 30-pin connector or a Universal Serial Bus (USB) connector may be inserted into the TA 1158. The TA 1158 may receive power from an external power source and charge the battery 1159 with the received power.

The IFPM 1157 processes the power received from the wired charging terminal and outputs the processed power to the battery 1159 and the PMIC 1153.

The PMIC 1153 manages power received wirelessly or wiredly and power applied to each component of the wireless power receiver 1150. The AP 1152 receives power information from the PMIC 1153 and controls the communication unit 1151 to transmit a PRU dynamic signal for reporting the power information.

A node 1156 connected to the WPIC 1154 is also connected to the TA 1158. If a wired charging connector is inserted into the TA 1158, a predetermined voltage, for example, 5V, may be applied to the node 1156. The WPIC 1154 determines whether the wired charging adaptor has been inserted by monitoring a voltage applied to the node 1156.

The AP 1152 has a stack of a predetermined communication scheme, for example, a WiFi/BT/BLE stack. Accordingly, for communication for wireless charging, the communication unit 1151 loads the stack from the AP 1152 and then communicates with the communication unit 1110 of the wireless power transmitter 1100, based on the stack, by BIBLE.

However, it may occur that data for wireless power transmission cannot be retrieved from the AP 1152 due to power-off of the AP 1152 or there is insufficient power to maintain an ON state of the AP 1152 during retrieval of the data from a memory of the AP 1152 and usage of the retrieved data.

If the residual power amount of the battery 1159 is below a minimum power limit as described above, the AP 1152 is turned off and the battery 1159 is wirelessly charged using some components for wireless charging in the wireless power receiver 1150, for example, the communication unit 1151, the WPIC 1154, and the resonator 1155. A state in which power sufficient to turn on the AP 1152 cannot be supplied may be referred to as a dead battery state.

Because the AP 1152 is not operated in the dead battery state, the communication unit 1151 may not receive the stack of the predetermined communication scheme, for example, the WiFi/BT/BLE stack from the AP 1152. In anticipation of this case, a part of the stack of the predetermined communication scheme, for example, a BLE stack, is fetched from the AP 1152 and stored in a memory 1162 of the communication unit 1151. Accordingly, the communication unit 1151 may communicate with the wireless power transmitter 1100 using the stack of the communication scheme stored in the memory 1162, that is, a wireless charging protocol, for wireless charging. The communication unit 1151 may have an internal memory. The BLE stack may be stored in a Read Only Memory (ROM) in the SA mode.

As described above, a mode in which the communication unit 1151 communicates using the stack of the communication scheme stored in the memory 1162 may be referred to as the SA mode. Accordingly, the communication unit 1151 may manage the charging procedure based on the BLE stack.

With reference to FIGS. 2 to 11, the concept of the wireless charging system applicable to the embodiments of the present invention has been described above. Below, methods for preventing occurrence of an abnormality according to embodiments of the present invention are described in detail with reference to FIGS. 12 to 15.

FIG. 12 is a flowchart illustrating an operation for preventing an abnormality during wireless charging according to an embodiment of the present invention.

According to an embodiment of the present invention, a single wireless power transmitter transmits charging power to a plurality of wireless power receivers. When the wireless power transmitter supplies charging power to the plurality of wireless power receivers, various algorithms may be used to determine transmission power of the wireless power transmitter, because the plurality of wireless power receivers may differ in terms of characteristics, states, and types.

For example, a minimum error (Vrect_setmin_error) tracking algorithm or a minimum power efficiency tracking algorithm is available to resonance-based wireless charging.

The minimum error tracking algorithm selects a wireless power receiver (that is, a PRU) having a highest power usage rate as a dominant wireless power receiver and controls a transmission power level of a wireless power transmitter (that is, a PTU) so that the difference between a Vrect value of the dominant wireless power receiver and a Vrect_set value indicated by a PRU static parameter may be minimized. The transmission power level of the wireless power transmitter may be controlled by controlling current Itx flowing through a coil.

The minimum power efficiency tracking algorithm controls a transmission power level of a wireless power transmitter to achieve a maximum efficiency by calculating a ratio between the sum of power consumed by a plurality of wireless power receivers and power supplied by the wireless power transmitter. The transmission power level of the wireless power transmitter may be controlled by controlling current Itx flowing through a coil.

Referring to FIG. 12, a wireless power transmitter (PTU) transmits wireless charging power to a plurality of wireless power receivers (PRUs) based on a power value determined according to a first mode (for example, a mode corresponding to the minimum error tracking algorithm) in step S1201.

If an abnormality (for example, over voltage, over current, or over temperature) is expected to occur in the wireless power transmitter or a wireless power receiver and thus a predetermined abnormality occurrence condition is satisfied during transmission of power from the wireless power transmitter to the plurality of wireless power receivers (for example, a predetermined threshold or a threshold range in which a system error occurs is reached) in step S1203, the wireless power transmitter switches from the first mode (for example, the mode corresponding to the minimum error tracking algorithm) to a second mode (for example, a mode corresponding to the minimum power efficiency tracking algorithm) in step S1205.

Therefore, the wireless power transmitter transmits wireless charging power to the plurality of wireless power receivers based on a power value determined according to the second mode in step S1207.

According to an embodiment of the present invention, if the abnormality such as over current, over voltage, or over temperature is overcome during power transmission in the second mode and thus a predetermined abnormality release condition is satisfied during power transmission in the second mode in step S1209, the wireless power transmitter switches from the second mode (for example, the mode corresponding to the minimum power efficiency tracking algorithm) to the first mode (for example, the mode corresponding to the minimum error tracking algorithm) in step S1211.

Therefore, the wireless power transmitter transmits wireless charging power to the plurality of wireless power receivers based on a power value determined according to the first mode in step S1213.

For example, if the wireless power transmitter approaches a threshold at which occurrence of a system error (for example, over voltage, over current, or over temperature) is expected and thus each measurement falls within a predetermined range during operating in the mode corresponding to the minimum error tracking algorithm, the wireless power transmitter operates in the minimum power efficiency tracking algorithm by switching to the mode corresponding to the minimum power efficiency tracking algorithm.

When the operation mode is switched as described above, the difference between a Vrect value of a dominant wireless power receiver determined by the minimum error tracking algorithm and a predetermined Vrect_set value may become broad, thereby decreasing the efficiency of the dominant wireless power receiver. However, as the efficiencies of the other wireless power receivers being charged increase, total efficiency may increase. Since Vrect values of the other wireless power receivers approach their Vrect_set values, the resulting increase in their efficiencies may lead to a decrease in voltage, current, or temperature, thereby preventing an occurrence of the abnormality.

If the system or a device is stabilized in this manner, the wireless power transmitter may switch from the mode corresponding to the minimum power efficiency tracking algorithm to the mode corresponding to the minimum error tracking algorithm.

FIG. 13 is a flowchart illustrating an operation for preventing an abnormality during wireless charging according to an embodiment of the present invention.

Referring to FIG. 13, a wireless power transmitter determines a transmission power value, taking into account a dominant wireless power receiver among a plurality of wireless power receivers in step S1301. The wireless power transmitter transmits wireless charging power to the plurality of wireless power receivers based on the determined power value in step S1303.

If an abnormality (for example, over voltage, over current, or over temperature) is expected to occur in the wireless power transmitter or a wireless power receiver and thus a predetermined abnormality occurrence condition is satisfied during transmission of power from the wireless power transmitter to the plurality of wireless power receivers (for example, a predetermined threshold or a threshold range in which a system error occurs is reached) in step S1305, the wireless power transmitter sets a wireless power receiver corresponding to the abnormality occurrence condition as the dominant wireless power receiver in step S1307.

The wireless power transmitter determines a transmission power value, taking into account the changed dominant wireless power receiver, in step S1309. The wireless power transmitter transmits wireless charging power to the plurality of wireless power receivers using the determined power value in step S1311.

According to an embodiment of the present invention, if the abnormality such as over current, over voltage, or over temperature is overcome and thus a predetermined abnormality release condition is satisfied during power transmission in consideration of the changed dominant wireless power receiver in step S1313, the wireless power transmitter resets the initial dominant wireless power receiver as a current dominant wireless power receiver in step S1315. The wireless power transmitter determines a transmission power value, taking into account the reset dominant wireless power receiver (that is, the initial dominant wireless power receiver), in step S1316, and transmits wireless charging power to the plurality of wireless power receivers using the determined transmission power value in step S1317.

According to an embodiment of the present invention, for example, if the wireless power transmitter determines transmission power according to the mode corresponding to the minimum error tracking algorithm, the wireless power transmitter selects a wireless power receiver having a high power usage rate as a dominant wireless power receiver from among a plurality of wireless power receivers and controls the transmission power in such a manner that a Vrect value of the dominant wireless power receiver approaches a Vrect_set value.

Since the minimum error tracking algorithm is designed so that a Vrect value of a specific wireless power receiver (for example, a dominant wireless power receiver) may track a Vrect_set value of the wireless power receiver, a Vrect value of at least one other wireless power receiver may diverge from a Vrect_set value of the wireless power receiver, in multi-charging. For this reason, a voltage, current, or temperature of the at least one other wireless power receiver may reach an error threshold.

For example, the above abnormal situation may occur more frequently in the following multi-charging cases in which:

1. a wireless power receiver coupled well to a wireless power transmitter and a wireless power receiver coupled poorly to the wireless power transmitter are charged at the same time;

2. the difference between the capacities of resonators in wireless power receivers is great; and

3. the difference between power classes (for example, categories) of wireless power receivers is great.

If such an abnormality occurs during multi-charging, the wireless power transmitter selects a wireless power receiver that approaches an Over Voltage Protection (OVP), Over Current Protection (OCP), or Over Temperature Protection (OTP) threshold as a dominant wireless power receiver from among a plurality of wireless power receivers, because the wireless power transmitter is monitoring charged states of the wireless power receivers. Accordingly, as the dominant wireless power receiver reaches an optimum operating range by making a Vrect value of the dominant wireless power receiver close to a Vrect_set value, the error situation may not occur.

If a Vrect of any other wireless power receiver reaches or falls below a Vrect_min value, charging of the wireless power receiver is discontinued. Therefore, even though the Vrect value of the dominant wireless power receiver does not reach the Vrect_set value, tracking is stopped at a point where the Vrect value of any other wireless power receiver is not below the Vrect_min value. In spite of the discontinued tracking, the probability of reaching an error situation may be reduced, because the wireless power transmitter has reduced Itx with respect to the transmitted power.

If the wireless power receiver close to an error situation is stabilized in this manner, the wireless power transmitter rests the wireless power receiver having the highest power usage rate in the original algorithm as a dominant wireless power receiver.

FIG. 14 is a flowchart illustrating an operation for preventing an abnormality during wireless charging according to an embodiment of the present invention.

Referring to FIG. 14, a wireless power transmitter transmits wireless charging power to a plurality of wireless power receivers in step S1401.

Upon sensing an occurrence of an abnormality (for example, over voltage, over current, or over temperature) in at least one wireless power receiver during power transmission to the plurality of wireless power receivers in step S1402, the wireless power transmitter transmits a power adjust command to the at least one wireless power receiver in step S1403.

According to an embodiment of the present invention, for example, the wireless power transmitter commands the wireless power receiver to reduce load current of the wireless power receiver by transmitting a power adjust command in a PRU control parameter as illustrated in Table 5 and Table 6 below.

TABLE 5 Field Octet Description Use Units Enables 1 PTU turn on. PTC Mandatory N/A on indication etc. Permission 1 PRU is permitted in Mandatory N/A PTU. Time Set 1 PTU sets up time. Mandatory ms RFU 2 Undefined N/A N/A

TABLE 6 7 6 5 4 3 2 1 0 Enable PRU Enable PRU Adjust power command RFU RFU RFU RFU output charge indicator 1 = Enable 1 = Enable 00 = Maximum power RFU RFU RFU RFU 0 = Disable 0 = Disable 01 = 66% * P_(RECT) _(—) _(MAX) 10 = 33% * P_(RECT) _(—) _(MAX) 11 = 2.5 W

If the wireless power receiver is capable of reducing its load current, the wireless power receiver reduces power consumption so that the wireless power transmitter may have extra power to charge another wireless power receiver or the wireless power receiver drops its current, voltage, or temperature.

If a current value Itx of power supplied by the wireless power transmitter is excessive during charging a plurality of wireless power receivers, it is highly probable that a wireless power receiver will face an error situation (e.g., over voltage, over current, or over temperature).

According to an embodiment of the present invention as described above, if the wireless power transmitter senses a wireless power receiver that may face an abnormal situation, that is, the wireless power receiver approaches an error threshold set for determining an error occurrence, the wireless power transmitter commands the wireless power receiver to reduce power required for the load of the wireless power receiver. According to an embodiment of the present invention, if the wireless power receiver is capable of power rationing, the wireless power receiver drops a voltage or current flowing in it or its temperature by reducing the power of its load.

FIG. 15 is a flowchart illustrating an operation for preventing an abnormality during wireless charging according to an embodiment of the present invention.

Referring to FIG. 15, a wireless power transmitter transmits wireless charging power to a plurality of wireless power receivers in step S1501.

Upon sensing an occurrence of an abnormality (for example, over voltage, over current, or over temperature) in at least one wireless power receiver during power transmission to the plurality of wireless power receivers in step S1503, the wireless power transmitter transmits a power reception stop command to the at least one wireless power receiver in step S1505.

According to an embodiment of the present invention, the wireless power transmitter commands the wireless power receiver to discontinue power reception by transmitting a power reception stop command in a PRU control parameter so that the wireless power receiver discontinues reception of power required for charging.

As the wireless power receiver discontinues power reception, the wireless power transmitter may have extra power to charge another wireless power receiver or the wireless power receiver may drop its current, voltage, or temperature.

As is apparent from the foregoing description, according to an embodiment of the present invention, since a wireless power transmitter expects various abnormalities that may occur during transmission of charging power to a plurality of wireless power receivers and appropriately handles the expected occurrences of abnormalities, the abnormalities can be effectively prevented.

According to an embodiment of the present invention, if the wireless power transmitter expects an occurrence of an abnormality in at least one wireless power receiver, the wireless power transmitter can prevent the abnormality by changing or modifying a charging algorithm.

According to an embodiment of the present invention, if the wireless power transmitter expects an occurrence of an abnormality in at least one wireless power receiver, the wireless power transmitter can prevent the abnormality by changing a dominant wireless power receiver.

According to an embodiment of the present invention, if the wireless power transmitter senses an occurrence of an abnormality in at least one wireless power receiver, the wireless power transmitter can prevent the abnormality by transmitting a power adjust command to the at least one wireless power receiver.

According to an embodiment of the present invention, if the wireless power transmitter senses an occurrence of an abnormality in at least one wireless power receiver, the wireless power transmitter can prevent the abnormality by transmitting a power reception stop command to the at least one wireless power receiver.

While the present invention has been shown and described with reference to certain embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope and spirit of the present invention as defined by the appended claims and their equivalents. 

What is claimed is:
 1. A control method of a wireless power transmitter, the method comprising: transmitting power to a plurality of wireless power receivers based on a first power value required by a first wireless power receiver from among the plurality of wireless power receivers; selecting, before reaching a threshold condition in which a system error occurs in the wireless power transmitter, a second wireless power receiver from among the plurality of wireless power receivers; and in response to the second wireless power receiver being selected, transmitting power to the plurality of wireless power receivers based on a second power value required by the second wireless power receiver, wherein the system error comprises at least one of an over-temperature error, an over-current error, and an over-voltage error.
 2. The method of claim 1, further comprising: transmitting a power adjust command to reduce the power to a lower percentage of a maximum received power level.
 3. The method of claim 1, wherein the over-voltage error is based on a measured voltage value exceeding a predetermined voltage value, the over-current error is based on a measured current value exceeding a predetermined current value, and the over-temperature error is based on a measured temperature value exceeding a predetermined temperature value.
 4. The method of claim 2, wherein the power adjust command is a control command for reducing power consumption of at least one wireless power receiver from among the plurality of wireless power receivers.
 5. The method of claim 2, wherein the power adjust command is included in a power receiving unit control signal.
 6. The method of claim 1, further comprising: measuring at least one value of a voltage value, a current value, and a temperature value in the wireless power transmitter; and determining that the system error is expected to occur when the at least one value of the measured voltage value, the measured current value, and the measured temperature value falls within a predetermined range indicating that the at least one value approaches the threshold condition set for determining whether the system error occurs.
 7. A wireless power transmitter for wirelessly charging a plurality of wireless power receivers, the wireless power transmitter comprising: a power transmitter configured to wirelessly transmit power to the plurality of wireless power receivers based on a first power value required by a first wireless power receiver; a communication unit configured to transmit a signal to the plurality of wireless power receivers; and a controller configured to: select, before reaching a threshold condition in which a system error occurs in the wireless power transmitter, a second wireless power receiver from among the plurality of wireless power receivers; and in response to the second wireless power receiver being selected, control the power transmitter to transmit power to the plurality of wireless power receivers based on a second power value required by the second wireless power receiver, wherein the system error comprises at least one of an over-temperature error, an over-current error, and an over-voltage error.
 8. The wireless power transmitter of claim 7, wherein the controller is further configured to transmit a power adjust command to reduce the power to a lower percentage of a maximum received power level.
 9. The wireless power transmitter of claim 7, wherein the over-voltage error is based on a measured voltage value exceeding a predetermined voltage value, the over-current error is based on a measured current value exceeding a predetermined current value, and the over-temperature error is based on a measured temperature value exceeding a predetermined temperature value.
 10. The wireless power transmitter of claim 8, wherein the power adjust command is a control command for reducing power consumption of at least one wireless power receiver from among the plurality of wireless power receivers.
 11. The wireless power transmitter of claim 8, wherein the power adjust command is included in a power receiving unit control signal.
 12. The wireless power transmitter of claim 7, wherein the controller is further configured to: control to measure at least one value of a voltage value, a current value, and a temperature value in the wireless power transmitter; and determine that the system error is expected to occur when the at least one value of the measured voltage value, the measured current value, and the measured temperature value falls within a predetermined range indicating that the measured at least one value approaches the threshold condition set for determining whether the system error occurs. 